Combination furnace and water heater



July 25, 1944. A. DOHERTY 2,354,507

' COMBINATION FURNACE AND WATER HEATER Filed Sept. 9, 1940 2 Sheets-Sheet 1 L an! 23 24 7 32 26 ms Q \\58 2 INVENTOR.

ARTHUR DOHE'RFY BY K ATTORNEY July 25, 1.944. A, DOHERTY COMBINATION FURNACE AND WATER HEATER 2 Sheet-Sheet 2 I Filed Sept. 9, 1940 INVENT OR.

AR THUR DOHERTV BY ATTORNEL Patented July 25, 1944 UNITED STATES PATENT OFFICE COMBINATION FURNACE AND WATER HEATER Arthur Doherty, Los Angeles, Calif.

Application September 9, 1940, Serial No. 356,016

9 Claims.

This invention relates to furnace construction, and more particularly to a combined hot air furnace and water heater.

An object of my present invention is to provide a combined furnace and water heater which represents an improvement over that forming the subject matter of my co-pending applicaion, Serial No. 340,865, filed June 17, 1940, issued as Patent No. 2,243,455, dated May 27, 1941, by so arranging matters that it utilizes a portion of the heat of the furnace to maintain the temperature of the water in the water heating system at or near the point desired for domestic use, and yet is so constructed that it provides definite assurance against overheating the water beyond the point generally considered to'be the maximum desirable temperature for hot Water for domestic purposes, even when the furnace portion of the device is operated at maximum capacity for long periods of time.

A more detailed object of the invention is to provide, in heating apparatus of the general character indicated, means for by-passing a portion of the cold air to be heated by the furnace, into an insulating chamben or passage, extending between the fiue which carries the heated products of combustion and the water heater. This cold air is thus enabled to absorb and carry away a portion of the heat which otherwise would be transmitted to the water heater to such an extent as to heat the water therein to a temperature in excess of that generally considered desirable; and inasmuch as the quantity of air caused to pass through the furnace increases when the load upon the furnace increases, the quantity of cold air thus circulated between the flue passage and the water heater correspondingly increases in accordance with increase in the heat output of the furnace, with the result that the device is largely self-regulating to supply cool air to the insulating chamber in quantities substantially proportional'to the need therefor.

A further object of the present invention is to combine the airpassing through the insulating chamber with the balance of the air heated by the furnace, with the result that none of the heat absorbed and carried away by the insulating air need be wasted, but is conducted to the apartment being served by the furnace.

Another object is to provide the by-passing means to which reference has already been made, in the form of a plurality of separate tubes, or flues, the number of which exceeds that required to provide ample cooling for the water heater intended foruse' under average conditions, but

all of which are available for use when unusual conditions of use are encountered which make it desirable to circulate a greater amount of coolingair through the insulating passage in order to provide assurance against overheating the water. This makes for standardizatiomas it permits construction of the heater in' but fasingle size and yet possessed of sufficient adaptability to regulation to fit it to many different'types of operating conditions. the performance of the experimental work leading tothe development'o'f the most efficient de-- sign, for it assists materially in ascertaining how much air should be by passed'through the insulating chamber and in providing'the; appropriate number of by-pass tubes to provide that quantity of air after the ideal rate of flow through the insulating chamber has been determined, without necessitating any radical alteration'bf th general design or dimensions of the heating apparatus.

The invention possesses other objects and'fe'a: tures of advantage, some of which, with-those enumerated, will be set forth in the following' de scription of the preferred embodiment'of thein vention illustrated in the drawings accompanying and forming a portion of the specification. It=is to be understood, however, that I do notlimit myself to the showing made by the said draw ings and specificatiomasI mayadopt'variatioris I of the preferred form within the scope of the invention as set forth in the claims. 5 Referring to the drawingsf Y j Figure 1 is a longitudinal, medial, vertical sectional view taken through heating apparatus embodying the principles of the present invention. The plane of section is indicated by the line |-l of Fig. 2, and the direction of view by the arrows. Figure 2 is a View in front elevation taken in" the direction of the arrow 2 of Fig. 1, portions of the structure being broken away and'shown in'section to reveal the interior construction. Figure 3 is a horizontal sectional view'takn on the line 33 of Fig. 2, with the direction of view as indicated. Figure 4 is a horizontal sectional view taken on the line 4--4 of Fig. 2, with the direction of View as indicated. 7

Specifically describing that embodiment of my invention which has'been chosen for illustration and description, my improved combinationfur nace and water heater comprises a suitable housing I 6 preferably having double walls I! and I8 having insulation material I9 therebetween. Within this housing I6 innerand outercasings This feature also aids in ing 2| is of cylindrical form, whereas the shell,

or radiating fin 23 immediately outside of the casing 2| is of square cross-sectional form, thus presenting a passage 24 of relatively great capacity as compared with the passages 26 and 21, all of the defining walls of which are of the same general cross-sectional form, as is best shown in Fig. 3. This is an important detail, and one which lends itself particularly toward the fulfillment of the objects of the invention, for

the reason that the large passage 24 is an insulating passage, intended to protect the elements within the inner casing 2| from excess heat; and, of course, by increasing the capacity of the passage 24 its efliciency in performing this function of insulating is materially enhanced.

Within the inner casing 2| a water heater 3| is mounted, this heater 3| comprising a suitable boiler 32 having supplyand outlet pipes 33 and 34, respectively, operatively associated therewith, and'a gas burner 36, the supply of fuel to which is adapted to be controlled by means of a thermostat 31 within the boiler 32 and operatively connected to the valve 38 in the fuel supply line 39 of the burner 36.

Preferably insulation material 4| is interposed between the boiler 32 and the inner casing 2|, for which purpose another cylindrical member 42, of

considerably smaller diameter than the inner casing 2| and disposed coaxially thereinside, is employed to retain the insulation material in place.

The bottom of the inner casing 2|; is closed by a horizontal partition 43; and inasmuch as it is quite close to the top 45 of the fiI'BlbOX 44, it has been found preferable to provide a rather thick layer 46 of insulation material upon the upper surface of the partition 43. The firebox communication between the firebox 44 and thefresh air inlet chamber 52 disposed therebelow. The firebox 44 'is, however, sufficiently smaller than the inside dimensions'of the housing Hi to permit the outermost passage 21 to communicate past the firebox with the fresh air inlet chamber 52,'as clearly shown in Figures 1 and 2. Preferably a suitable fan 53 within the air chamber and driven by a motor 54, is employed to induce a forced draft upwards through the outermost passage '21 to a plenum 56 at the top of the housing l6, whence the air heated as the result of its contact with the .casing 22 defining the outer wall of the flue passage 26 as it rises within the furnace, is conducted to one or more distributing ducts 51. I

This construction thus far described resembles that forming the subject matter of my copending application identified above, in both general arrangement of its constituent parts and mode of operation. The principal change which has been made in the present apparatus, however, is that means are provided for circulating cold air through the insulating passage 24, so as to disperse at least some of the heat which otherwise would accumulate to such an extent as to raise the temperature of the water within the boiler 32 to an undesirable temperature if the furnace portion of the apparatus is operated atfull load for an extended period. It was found that without such circulation of cold air throughout the insulating passage 24, too much heat was transmitted to the water heater from the furnace, in spite of the fact that the underlying principle of the combined apparatus is to utilize a portion of the heat from the furnace to keep the water within the hot water system at or near the desired temperature so that the water heater burner 36 is brought into operation only when sufficient hot water is withdrawn from the boiler tolower its temperature suddenly. So eflicacious toward this end did the apparatus of my prior application prove, that the water within the hot water system would, within only a few hours of continued operation of the furnace, rise to a temperature in excess of that stipulated as the maximum safe temperature for a domestic hot water supply by the American Gas Association, even without any operation whatsoever, of the water heater burner 36.

In; the present apparatus this overheating of the water is avoided, as already indicated, by circulating cool air through the insulating passage 24. To accomplish this, the passage 24 is placed in communication with the plenum 56 by means of a conical duct 6|; and a plurality of tubes 62 extending upwards from the partition 5| through the firebox 44 and through the top 45 of the firebox to empty into the insulating passage 24 serve to supply cool air from the chamber 52. Of course this air will be raised somewhat in temperature because of its passage through the firebox 44 by way of the tubes 62, but not to the degree which would be attained by the air within the passage 24 in the absence of any circulation therethrough.

Of greater importance, however, than the mere fact that I have provided means for lowering the maximum temperature to which the water within the boiler will be raised by the heat of the furnace, are the regulatory measures made possible :by the plurality of tubes 62, any number of which may be employed to attain just that degree of cooling eiTect that may be desired to meet any given set of operating conditions. It will be observed that a relatively large number of small tubes 62 are provided, instead of a smaller number of tubes of greater individual capacity; and that a few of these tubes are blanked off, or plugged, as by means of a tapered plug 63 driven into one end of each tube 62 which it is desired to render inoperative. The explanation for this arrangement lies in the fact that by providing more tubes than necessary to provide the necessary cooling in the case of the average installation, it is made easily possible to meet such unusual conditions as might require greater than average cooling merely by leaving more of the tubes 62 open than in the usual case, and thus avoid the necessity for apparatus of different design from that capable of satisfying the usual requirements. ;'I'his,of course, tends to decrease operating-and marketing costs, by reducing the number of stock sizes of apparatus which must be kept on hand. Furthermore, it aids in great "measure inthe development work which must be conducted to ascertainjust how much cooling air must be permitted tojcirculate through the insulating passage 24 in order to maintain the water at the precise'deg'ree desired, without having to construct and operate a large number oi experimental models. Y Iclaim: 1'. A-combined'furnacefand water heater comprising a" housing, inner and outer casings disposed therein, "a radiating shell" interposed" between said casings and' spaced'from'both to pre- {sent passagesindepende'nt of each other, said outer casing being spaced from said housing to provide a third passage outside said other two, a boiler disposed within said inner casing, supply and outlet pipes communicating therewith, a firebox disposed below said radiating shell and communicating with the intermediate one of said passages, means providing an air inlet below said firebox and communicating with the outermost one of said passages, and means providing a bypass for air from said inlet to the innermost one of said passages to absorb a portion of the heat which otherwise would reach said boiler from flue gases within said intermediate passage.

2.. A combined furnace and water heater comprising a housing, inner and outer casings disposed therein, a radiating shell interposed between said casings and spaced from both to present passages independent of each other, said outer casing being spaced from said housing to provide a third passage outside said other two, a boiler disposed within said inner casing, supply and outlet pipes communicating therewith, a firebox disposed below said radiating shell and communicating with the intermediate one of said passages, means providing an air inlet below said firebox and communicating with the outermost one of said passages, means providing a bypass for air from said inlet to the innermost one of said passages to absorb a portion of the heat which otherwise would reach said boiler from flue gases within said intermediate passage, and means for regulating the capacity of said by-pass to predetermine the amount of heat permitted to reach said boiler.

present passages independent of each other, said outer casing beingspa'ced from said housing to provide a third passage outside said other two,"a-boiler disposed within said inner casing,

supply and outlet pipes communicating therewithga firebox disposed below said radiating shell and communicating with the intermediate one of said passages, means providing an air inlet be low said firebox and communicating with the outermost one of said passages, means providing a by-passof predetermined capacity to conduct air from saidinlet to said innermost passage to 'predetermine the maximum amount of heat to reachsaid boiler from flue gases within said intermediate; passage, and means providing a plenum into which both said outermost and said innermost passages lead. I v

' 5. A combined furnace and water heater com- "prising a" housing, inner and outer casings dis-'- 20 tween 'said casin'gs and spaced from both to posed therein, a radiating shell interposed bepresent passages independent of each other, said outer casing being spaced from said housing to provide a third passage outside said other two, a boiler disposed within said inner casing, supply and outlet pipes communicating therewith, a firebox disposed below said radiating shell and communicating with the intermediate one of said passages, means providing an air inlet below said firebox and communicating with the outermost one of said passages, means providing a by-pass of predetermined capacity to conduct air from said inlet to said innermost passage to predetermine the maximum amount of heat to reach said boiler from flue gases within said intermediate passage, and a burner associated with said boiler to heat its contents independently of said firebox. I

6. A combined furnace and water heater comprising a housing, inner and outer casings disposed therein, a radiating shell interposed between said casings and spaced from both to present passages independent of each other, said outer casing being spaced from such housing to provide a third passage outside said other two, a boiler disposed within said inner casing, supply and outlet pipes communicating therewith, a firebox disposed below said radiating shell and communicating with the intermediate one of said 3. A combined furnace and water heater comprising a housing, inner and outer casings disposed therein, a radiating shell interposed between said casings and spaced from both to present passages independent of each other, said outer casing being spaced from said housing to provide a third passage outside said other two, a boiler disposed within said inner casing, supply and outlet pipes communicating therewith, a firebox disposed below said radiating shell and communicating with the intermediate one of said passages, means providing an air inlet below said firebox and communicating with the outermost one of said passages, means providing a by-pass for air from said inlet to the innermost one of said passages to absorb a portion of the heat which otherwise would reach said boiler from flue gases within said intermediate passage, and means providing a plenum into which both said outermost and said innermost passages lead.

4. A combined furnace and water heater comprising a housing, inner and outer casings disposed therein, a radiating shell interposed between said casings and spaced from both to passages, means providing an air inlet below said firebox and communicating with the outermost one of said passages, means providing a by-pass of predetermined capacity to conduct air from said inlet to said innermost passage to predetermine the maximum amount of heat to reach said boiler from flue gases within said intermediate passage, a burner associated with said boiler to heat its contents independently of said firebox, and a thermostat within said boiler and operatively associated with said burner.

7. A combined furnace and water heater comprising a housing, inner and outer casings disposed therein, a radiating shell interposed between said casings and spaced from both to present passages independent of each other, said outer casing being spaced from said housing to provide a third passage outside said other two, a boiler disposed within said inner casing, supply and outlet pipes communicating therewith, a firebox disposed below said radiating shell and communicating with the intermediate one of said passages, means providing an air inlet communieating with the outermost one of said passages,

th heat which otherwis would reachs id boiler from, said intermediate passage.

BitAcOmbined-furnaCe and water heater-comprising a housing, inn'erand outer .casings dis: posed therein, a radiating shell interposedbetween said casings and spaced. from both ,to present passages independent of each other, said outer casing being spaced from said housing to provide a third passage outsidesaid' other two, a boiler disposed within said inner casing, supply .and .outlet pipes communicating therewith), a

firebox disposed below said radiating shell and communicating with the-intermediate one of said passages, means providing an air inlet communimeans for circulating air through the innermost one of said passages to absorb a portion of the 1 heat which otherwise would reach said boiler 19; -;A combined furnace and water heater comprisinga housing, inner and outer casings disposedtherein, a radiating shell interposed between said casings and spaced from both to present passages independent of each other, said outer casing being spaced from said housing to provide a third passage outside-said other two, a boiler disposed within said'inner casing, supply and outlet pipes communicatingtherewith, a source ofvheat communicating with the inter mediate one of said passages, means providing an air inlet communicating with the outermost one of said passages,.means for circulating, air

and means providing a plenum into which both said outermost and said innermost passages lead.

' ARTHUR DOHERTY. 

